This article outlines an approach to bridging the gap between the theory and practice of differentiated instruction. Differentiated instruction has long been suggested as a pedagogical approach to cater for student individuality and diversity, particularly in mixed-ability classrooms. Although the theory of differentiated instruction has been applied widely, such instruction has not been taken up widely in teaching practice. The first part of the article explores the relationship of theory and practice of differentiated instruction in relation to pedagogical content knowledge, teacher efficacy, formative assessment, teacher confidence and competence and professional learning. This exploration uses exemplar cases from mathematics teaching to pave the way for an outline, in the second part of the article, of how differentiated instruction could be implemented for the mixed-ability groupings increasingly engaged in the Australian secondary mathematics classroom. A protype practice framework for teachers is presented as part of a project being conducted in regional Australia, with the overall aim of assisting teachers in developing and implementing strategies for differentiated instruction in secondary mathematics classrooms.